Conventionally, as digital apparatus become highly functional and communication terminals capable of using a wireless LAN (Local Area Network) become widely available, a technology for transmitting large-volume data (for example, HD (High Density) video data) by making communication terminals communicate with each other without interposing an access point, for example, is attracting attention.
However, in the case that large-volume data is transmitted using a wireless LAN, a transmitter compresses transmission data and a receiver decompresses received data, whereby a slight delay occurs. Hence, in an application required to operate in real time, the video transmission according to the conventional technology in which data is compressed and decompressed each time large-volume data is transmitted has not been efficient.
Hence, at present, high-speed wireless communication capable of transmitting uncompressed and non-delay video data using a millimeter wave (for example, 60 [GHz]) is receiving attention.
Millimeter wave communication uses a band wider than that of the wireless LAN communication. High-speed wireless communication, for example, using a wave of 1 [GHz] or more becomes possible by effectively using the allowable range of millimeter wave communication. However, since the electromagnetic wave of the 60 GHz millimeter wave band is long in wavelength and high in rectilinearity and is apt to be absorbed by oxygen molecules in the atmosphere, it is pointed out that the 60 GHz millimeter wave is unsuited for long distance transmission.
On the other hand, the distance of communication can be extended by using beam forming in which the direction of the beam is changed electronically by arranging a plurality of antenna elements and by controlling the phases of the transmission wave and the received wave at each antenna element. However, when an obstacle (for example, a human hand) intervenes between the communication terminals during wireless communication, the communication may be interrupted.
A wireless communication apparatus is known in which, for example, in the case that the communication characteristic of line-of-sight communication, that is, communication using a direct wave, was degraded by an obstacle, communication interruption is avoided by changing the rotation direction of the circularly-polarized wave being used for wireless communication (for example, refer to Patent Document 1).